1. Field of the Invention
The present invention relates to a lens driving apparatus and an optical apparatus having the same.
2. Description of the Related Art
One conventionally known driving unit for a focusing or zooming lens holding frame includes a motor having a lead screw, and a rack unit that is coupled with the lens holding frame, mated with the lead screw, and configured to move along the lead screw as the motor rotates.
Japanese Patent Laid-Open No. (“JP”) 4-240609 discloses a configuration of a rack unit that includes two sub-units and is forced against a lead screw by a spring member.
JP 9-258087 discloses a rack unit that includes a mated portion, a forcing portion, and an opposed cog. The mated portion is arranged on one side of the lead screw, and the forcing portion is arranged on the other side. The mated portion is mated with the lead screw, and the fixed opposed cog is arranged on the opposite side of the mated portion and is offset in the optical-axis direction from the mated portion so as to prevent a cog skip (positional shift) upon impact. In addition, at an end of a movable range of the rack unit, an opposed cog is located at a non-threaded area of the lead screw so as to prevent cogging of the rack unit at the end of the movable range of the lens holding frame.
In the structure disclosed in JP 4-240609, the spring member must apply a considerable force in order to prevent a positional shift between the rack unit and the lead screw upon impact. Then, a load of the motor increases, a large and high-torque motor is required, and a larger size and an increased cost of the apparatus become problematic.
In the structure disclosed in JP 9-258087, a strong impact at the position other than the end of the movable range of the lens holding frame would cause a plastic deformation (cogging) between the mated portion and the lead screw, and at least one of the mated portion and the lead screw get damaged and become inoperable.